Fate of inhaled nitrogen dioxide in isolated perfused rat lung

Abstract

The fate of Inhaled NO₂ was studied with isolated perfused rat lungs. The isolated lungs were exposed to 5 ppm NO₂ for 90 min at a ventilation rate of 45 ml/min. The NO₂ exposure had no adverse effects on the lungs as judged from their weights, glucose uptake, or lactate production compared to control lungs. Isolated lungs absorbed 36% of ventilated NO₂, which was detected in perfusate and lung tissue as NO₂ ⁻ but not NO₃ ⁻. The NO₂ ⁻ concentration in perfusate increased linearly with time, and after 90 min of ventilation with NO₂ and perfusion with erythrocyte‐free medium the NO₂ ⁻ accumulation was 6.36 ±0.39 μg. If perfusate contained 10% erythrocytes, the ventilated NO₂ product was mostly NO₃ ⁻ in perfusate but NO₂ ⁻ in lung tissue. Protein solutions absorbed N0₂ more effectively than simple salt solutions, but they all yielded mainly N0₂ ⁻ unless erythrocytes were present, when the product was mostly NO₃ ⁻. The results indicate that absorbed NO₂ in the lung is converted predominantly to NO₂ ⁻, but after its diffusion into the vascular space it is oxidized to NO₃ ⁻ by interactions with erythrocytes.